Langjam #0001

Theme: first-class comments

Concept

Conceptually, the main ideas for this language were

• making comments available at runtime, as metadata attached to various elements of the code
• allowing modification, addition and removal of comments at runtime
• allowing comments to contain expressions, e.g. greaterThan(_, 5), which will be parsed in the same way as the rest of the language
• allowing execution of comments based on the comment type, e.g. an assert comment on a variable, which would be executed every time the variable changes.

Unfortunately there wasn't enough time to implement most of this functionality, but this is what it might have looked like:

fn area(
  <assert: greaterThan(a, 0)>
  a,
  <assert: greaterThan(b, 0)>
  b
) {
  multiply(a, b)
}

print(area(5, 10))
print(area(-1, 10))

When running this example, the expected result would have been:

50
Error: Assertion on `a` – greaterThan(a, 0) – failed. `a` was -1.

What was actually achieved

The language supports attaching comments to identifiers and accessing them at runtime:

fn i_like(
    <indicates which thing you like> the_thing,
) {
    let x = "I like "
    print(the_thing.$comment)
    print(length(the_thing.$comment))
    concat(x, the_thing)
}

print(i_like("turtles"))

This snippet should result in

# => String("indicates which thing you like")
# => Integer(30)
# => String("I like turtles")

Building

Requirements

• cargo and Rust need to be installed
  • Tested with rustc 1.54.0 (a178d0322 2021-07-26)

Building

cargo build will build the target/debug/langjam0001 binary.

Testing

Run ./go test to see if all examples in the test/ directory can be run successfully. Doesn't currently test whether the output is correct 😶

Properties of the language

In no particular order

• Comments can be specified in pointy brackets <the comment>, and can be placed before statements and expressions (the idea is "everywhere")
• The following built-in functions exist: print, plus, multiply, length, concat.
• There are no operators
• Conditions also did not make the cut 😅
• The return value of a function is the return value of its last expression